layer_scroll_offset_delegate.h revision 5d1f7b1de12d16ceb2c938c56701a3e8bfa558f7 
1// Copyright 2013 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef CC_INPUT_LAYER_SCROLL_OFFSET_DELEGATE_H_
6#define CC_INPUT_LAYER_SCROLL_OFFSET_DELEGATE_H_
7
8#include "base/basictypes.h"
9#include "ui/gfx/size_f.h"
10#include "ui/gfx/vector2d_f.h"
11
12namespace cc {
13
14// The LayerScrollOffsetDelegate allows for the embedder to take ownership of
15// the scroll offset of the root layer.
16//
17// The LayerScrollOffsetDelegate is only used on the impl thread.
18class LayerScrollOffsetDelegate {
19 public:
20  // This is called by the compositor to notify the delegate what is the upper
21  // total scroll offset bound.
22  virtual void SetMaxScrollOffset(const gfx::Vector2dF& max_scroll_offset) = 0;
23
24  // This is called by the compositor when the scroll offset of the layer would
25  // have otherwise changed.
26  virtual void SetTotalScrollOffset(const gfx::Vector2dF& new_value) = 0;
27
28  // This is called by the compositor to query the current scroll offset of the
29  // layer.
30  // There is no requirement that the return values of this method are
31  // stable in time (two subsequent calls may yield different results).
32  // The return value is not required to be related to the values passed in to
33  // the SetTotalScrollOffset method in any way however it is required to be no
34  // more than the value passed to the most recent SetMaxScrollOffset call.
35  virtual gfx::Vector2dF GetTotalScrollOffset() = 0;
36
37  // This is called by the compositor to check whether a delegate-managed fling
38  // is active or not.
39  virtual bool IsExternalFlingActive() const = 0;
40
41  // This is called by the compositor to notify the delegate what is the current
42  // page scale factor and limits are.
43  virtual void SetTotalPageScaleFactorAndLimits(
44      float page_scale_factor,
45      float min_page_scale_factor,
46      float max_page_scale_factor) = 0;
47
48  // This is called by the compositor to notify the delegate what is the layer's
49  // scrollable size is.
50  virtual void SetScrollableSize(const gfx::SizeF& scrollable_size) = 0;
51
52 protected:
53  LayerScrollOffsetDelegate() {}
54  virtual ~LayerScrollOffsetDelegate() {}
55
56 private:
57  DISALLOW_COPY_AND_ASSIGN(LayerScrollOffsetDelegate);
58};
59
60}  // namespace cc
61
62#endif  // CC_INPUT_LAYER_SCROLL_OFFSET_DELEGATE_H_
63